The present invention relates to optical disk players and more particularly to the tracking mechanism for optical sensing devices.
In certain optical disk players optical sensing of a spiral track or alternatively circular tracks on the disk is accomplished by reflecting light off the surface of the disk and onto a photo-optic sensor. One way of tracking in such an optical recorder is to move the photo-optic sensor radially inward as the disk rotates so the photo-optic sensor scans the entire disc. One problem with such a tracking and sensing system is that because of manufacturing tolerances and other problems the spiraling of the track is not uniform but has eccentricities. These eccentricities cause cross talk in the optically sensed data and also cause the skipping of certain sections of the track while repeating other sections of the track.
In the past many systems have been proposed to permit the photo-optic sensor to track data recorded with the described eccentricities. One such tracking system involves the use of mirrors. As shown in U.S. Korpol Pat. No. 3,931,459 a mirror directs light through a disc into two photo sensitive devices to generate outputs which are summed to generate the output for the video disc player and which are subtracted to generate a tracking control signal for positioning the mirror. Another tracking system uses a string of photosensitive devices for tracking. U.S. Pat. Nos. 3,158,846 and 3,780,266 both describe an array of photo-optic devices with circuitry that is responsive to the diodes outputs to switch connections for tracking purposes.